Biochemical composition of seeds and nitrogen consumption by the crops of different soybean varieties

The purpose of the current study was to identify the impact of phosphorus-potassium nutrition on the dynamics of soybean seed chemistry in the forest-steppe part of the Chechen Republic. The objects of the study were the promising soybean varieties Amadeus, SG SR Pikor, and Smuglyanka. Between 2022 and 2024, leached chernozems sown with soybean were supplied with various levels of available phosphorus and potassium. There has been established that the rate of mineral fertilizer Р 90 К 60 was optimal for soybean crops under these environmental conditions, as it provided the best conditions for legume-rhizobial symbiosis. This, in turn, enhanced nitrogen accumulation in various plant parts. During the phase of bean formation, the leaves had the highest nitrogen concentration of 2.09–3.11%, while in the stems and root system, this value ranged from 0.97–1.68% and 0.78–1.03%, respectively. The nitrogen content in nodules was 2.46–4.69% during the flowering period, 3.03–4.80% during the phase of bean formation, and 1.94–3.29% during the period of bean filling. The fertilized background has increased the protein and oil percentage in beans, and this trend was characteristic of all the studied varieties. Protein yield in the control variant ranged from 877.6 to 1039.6 kg/ha, and in the fertilized background it varied from 989.8.4 to 1158.7 kg/ha. Similar indicators for oil yield were from 479.8 to 598.8 kg/ha and from 537.9 to 658.3 kg/ha. Peak dry matter accumulation in plant organs occurred during the phase of bean formation, with the bulk of the dry matter concentrated in the leaves and stems. During the period of bean filling, the proportion of dry matter accumulated in beans reached its maximum values of 1027.1–1651.3 kg/ha. Nitrogen consumption by crops has raised throughout the vegetation period and reached its maximum values by the period of bean filling with 66.48–106.48 kg/ha in the control variants and 99.03–137.70 kg/ha in the fertilized variants.